SOLAR WIND RIPS MARS: The solar wind appears to be ripping big chunks of air from the atmosphere of Mars. This could help solve a longstanding mystery about the Red Planet: full story.

SASKATCHEWAN FIREBALL: A brilliant green fireball startled onlookers across western Canada on Nov. 20th (5:30 pm MST) when it split the evening sky and fragmented during a series of thunderous explosions. "The sky was lit up almost like daytime for 3 or 4 seconds," reports Gordon Blomgren of Alberta. Murray McDonnell of northwestern Saskatchewan says "my wife and I saw a brilliant flash of blue white light, like lightning. About one minute later a long rumbling sound shook the house."

Andy Bartlett video-recorded the event from a 10th-floor apartment in Edmonton, Alberta:

"The brilliant fireball appeared to be closer than the airplane in the upper right corner of this video," says Bartlett. "I made the movie using a Canon A510."

The fireball was almost certainly a small asteroid disintegrating in Earth's atmosphere. A space rock measuring a few to ten meters wide moving at typical local-asteroid velocities would account for the fireball's speed and brightness. Reentry of manmade space junk has now been ruled out. Fragments of the impactor may have reached the ground; if so, they remain undiscovered and/or unreported.

VIDEO UPDATE: A spectacular video of the fireball was recorded by the dashboard camera of a police car on patrol in Edmonton, Alberta. Click to play.

FALSE AURORAS: Warning: Not all northern lights are aurora borealis. Consider the following display of "false auroras" over Ambler, Pennsylvania, on Nov 19th:

"Luminous vertical spikes emanated down from all areas of the sky," reports photographer Herman Fala. "They looked like Northern Lights, but did not seem to be moving or shimmering as I expected auroras to do." Furthermore, solar activity was low and no geomagnetic storm was in progress at the time of the display.

What Fala witnessed was an apparition of urban light pillars. Plate-shaped ice crystals flutter down from high clouds and intercept the rays of unshielded city lights, creating an aurora-like display that truly has nothing to do with auroras. Light pillars are beautiful but they are also a sign of spreading light pollution that threatens to wipe genuine auroras (and stars and planets and comets) out of the night sky forever. Enjoy them, but also be mindful of their dark significance.

High-latitude sky watchers should be alert for real auroras next week. A solar wind stream is heading for Earth and it could spark geomagnetic storms when it arrives on Nov. 24th or 25th.

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.